A power tool that can be connected to a battery pack is well known in the art (see PLT 1, for example). When a power tool of this type receives an overdischarge detection signal or an overcurrent detection signal from the battery pack, the power tool instantly halts rotation of the motor.
On the other hand, battery packs housing secondary battery cells are commonly used to power electric equipment and have been used extensively as the driving power source for power tools in particular. Various proposals have been made for this type of battery pack, aiming at eliminating the battery pack malfunctions that are caused by discharge current and may occur when the battery pack is used as a driving power source for a power tool.
For example, one technology proposed for reducing the occurrence of battery pack failure caused by overcurrent (PLT 2) outputs a halt signal to halt driving of the power tool when the discharge current from the battery pack exceeds an overcurrent threshold at which the discharge current is judged to be excessive. The outputted halt signal interrupts the drive of the power tool and electrical discharge from the battery pack.